Networks such as asynchronous transfer mode ("ATM") networks are used to transfer audio, video and other data. ATM networks deliver data by routing data units, such as ATM cells, from source to destination through switches. Switches include input/output ("I/O") ports through which ATM cells are received and transmitted. Each of the I/O ports, in turn, has at least one queue associated therewith for temporarily storing, or buffering cells processed by the respective port. Queues associated with an input port are referred to herein as input port queues and queues associated with an output port are referred to herein as output port queues.
Cells and control signals may be transmitted from an input port queue to a single output port queue in the case of point to point connections or from an input port queue to a selected group of output port queues in the case of point to multipoint connections. Prior to transmitting a cell from an input port queue to a destination output port queue, or queues, a control signal is sent from the input port to the destination output port, or ports, to query whether sufficient output port queue space is available to enqueue the cell.
In accordance with one type of ATM transmission, which may be referred to as "per-VC queuing", the cell header identifies the input port queue which temporarily stores the cell. In this way, the header also identifies the destination output port queue, or queues, since the cells stored in a particular input port queue have the same destination output port queue, or queues.
The ATM switch requires memory for storing a look-up table containing connection topology information (i.e., the destination output port queue, or queues associated with each input port queue). As the number of input and output ports increases, the size and bandwidth requirements of the connection topology memory likewise increase. Additionally, scaling the number of ports of the switch requires an increase in size of the connection topology look-up table.